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🔥Decode Ways: Numerical Cipher DPMedium
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MediumDynamic Programming•Acceptance: 34.5%

Decode Ways: Numerical Cipher DP

Targeted in FAANG & Tech OA:AmazonMicrosoftGoogle
Real-World Engineering Context
Used in variable-length prefix code decoders (Huffman coding), telecommunication binary framing, and cryptographic protocol ciphers.
A message containing letters from `A-Z` can be encoded into numbers using the mapping: 'A' -> '1', 'B' -> '2', ..., 'Z' -> '26'. To decode an encoded message, all the digits must be grouped then mapped back into letters. Given a string `s` containing only digits, return the number of ways to decode it. Note that `'06'` cannot be decoded into `'F'` because `'06'` is not a valid 2-digit number.

Sample Test Cases

Input: ["12"]
Expected: 2
Input: ["226"]
Expected: 3
Input: ["06"]
Expected: 0

Constraints

  • 1 <= s.length <= 100
  • s contains only digits and may contain leading zero(s).
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